Mat dryer humidity control system



OCU 18, 1966 J. J. RUDIGIER, .JR 3,279,089

MAT DRYER HUMIDITY CONTROL SYSTEM Filed July l, 1963 BY/yb/Mw ATTORNEY United States Patent 3,279,089 MAT DRYER HUMDITY ACONTROL SYSTEM Joseph J. Rudigier, Jr., Bethesda, Md., assignor to Hygrodynamics, Inc., Silver Spring, Md. Filed July 1, 1963, Ser. No. 291,712 5 Claims. (Cl. 34-45) This invention relates to drying apparatus, and more particularly to apparatus for controlling -the moisture content in mats which are used to cast ltype in a roto-grav-u-re press for printing newspapers and for other high speed print-ing applications.

A main object of the invention yis to provide a novel and improved apparatus ifor controlling the moisture content in a mat dried over a curved platen which 'has holes through -it communicating 'with a vacuum system, lthe apparatus involving relatively simple components, being reliable in operation, and providing close control of the humidity of the mat, so that the drying cycle will terminate automaticallyY when the humidity in the mat has decreased to a predetermined desired value.

A further object of the invention is to provide an improved humidity control apparatus for a 'mat dryer, the apparatus requiring inexpensive components, being relatively compact in size, and providing automatic and etcient control of the drying cycle of thel mat dryer, and taking into account Vthe humidity in Ithe lroom containing the mat dryer.

A still further object of the Iinvention is to provide an improved control apparatus vfor a mat dryer employed .to form and dry mats used to cast type for high speed printing operations, the control lapparatus being arranged to govern the operating cycle of a Ivacuum pump used in conjunction with heating means to shape and dry the mats, as -Well as to automatically open the dryer for removal of the mats when the drying cycle of the mats has been completed.

[Further objects and `advantages of the invention will become apparent from the following description and claims, and `from the accompanying drawing, wherein the single gure is a wiring diagram showing the electrical connections oi an improved humidity control system `for a mat dryer in accordance with the present invention. c

Referring to the drawing, 1'1 generally designates a machine for drying a lmat 12 used to cast type in a v,rotogravure press for printingnewspapers or for similar high speed printing applications. The machine V11 is of conventional mechanical construction and includes an apertured curved platen, shown diagrammatically at 13, through which air, :heated by heating coils 14, is drawn throughthe perforated concave bottom wall of a hollow 'hinged cover 15 by means of a vacuum pump 16. As shown, the hinged cover ,15 has a rotatable air connection joint, indicated diagrammatically -at 17, communicating with a conduit 18 provided with a filter unit 19, said conduit y18 leading to the inlet port of the vacuum pump 16. The cover '15 is provided with a counterweight 20 which biases the cover toward an open position, as is shown in dotted view, the cover being held in its closed position by a latch 21 en-gageable over a projection 22 onfthe free edge of the cover, the latch being biasedtoward locking'position by a spring 23. The ste-m 24 of the latch is secured to the plunger 25 of a solenoid 216, which when energized moves the latch outwardly to disengage it vfrom lprojection 22 land to thereby release the cover.

To dry the mat 12 itis iirst placed Iagainst .the concave inner side of the cover 15, after which the c over :is closed to the position shown in ll line view in the gure, whereby heated air may be drawn through themat by the vacuum pump 16. As willl be presently described, the drying cycle will terminate automatically when -the hu- 3,279,089 Patented Oct. 18K, 1966 midity `in the mat has decreased to la predetermined de sired valu'e.-

The control syste-m fof the mat dryer includes a start switch S1' of the slow-opening type, which, after being manually closed, opens after a predetermined time period, for example, 15 seconds. The system further includes a relay R1, motor-operated timers M1, M2 and M3, `further relays R2, R2, R4, R8 and R9, a three-fway'solenoid-operated air valve 27, and a thermostatically controlled heated bath unit 28 containing a bifilar-wound humidity sensing uni-t 29, all of which will be presently described in detail. Timer M1 has the three driven rotor elements 30, 31 and 32.. Rotor element 3l) carries a peripheral contact 33 engageable by a -iiXed contact `34. Rotor element G1 has spaced peripheral contacts 35 and 36 sequentially engageable by a lixed contact 37. Rotor element 36 has a peripheral contact 38 engage'able by a vfixed contact 39.

Timer `M2 has the three driven rotor elements 40, 41 and 42. Rotor element 40 carries the peripheral contact 43 engageable by`a xed contact 44. Rotor element 41 carries the peripheral contact 4S engageable by a fixed contact 46. Rotor 'element 42 carries -a peripheral contact 47 engageable by a ixed contact 48. YThe rotors'of the timers M1 and M2 are biased toward the starting positions shown Vin the figure by suitable spring means, such `as the spiral biasing springs 49' and 50 diagrammatically illustrated. i v v Timer M3 drives a cam disc 51 havin-g a peripheral notch 52. Said disc isl engaged by a follower lug'on a pivoted switch pole 53 engageable with a xed contact 54 except when said `follower lug engages in the notch 52, which is the normal starting position. Timer M3 also drives the adjustable contact 55 of a rheostat 56. Said rheostat is connectedin a manner to regulate the bias potential on `the control grid V57 of a vacuum tube 58 in -a circuit similar to that disclosed in U. S. Patent No. 2,943,245, to C. E. Ohlheiser, entitled Humidity Control Device. The relays R2 and R3 are Yconnected in circuit with the plate 59 of said tube, said relays having dilerent sensitivities. The humidity sensing element 29 is connected in circuit with said grid 57 ina manner to cause the plate current of tube 58,10 drop with increasing humidity, and conversely, lto cause said plate current to increaseV with decreasing humidity. When the plate current increases, relay R3 closes iirst, `and Vrelay -R2 c loses subsequently, with continued increase in plate current. Similarly, when the humidity' increases, relay R3 becomes deenergized rst, followed subsequently by the deenergization of relay R2 as the 'humidity continues to increase.

The b ath 28 contains a tempering coil 60 connected at one end to the upper portion of a chamber 61 containing the humidity sensing element 29. The other end of said coil 60 is connected through the three-way valve 27 to a conduit 62 leading to the air space 17. Three-way valve 27 has a port 63` exposed tn atmosphere. The valve rotor 64, in the derenergized condition of solenoid 65, connects coil 60 to atmosphere port `63. When the solenoid 65 of the valve is energized, rotor 64 is turned so asto connect coil 60 to the conduit 62. Y

The lower endof chamber 61 is connectedby a conduit 66 to conduit 18 `adjacent pump 16.

Bath 28 is provided with suitablethermostatically controlled heating means to maintainv a predetermined liquid temperature therein for example, F.

A manually controlled two pole switch 67 is provided, said s witch having a lower movable pole 68 normally engaging a pair of contacts 69 and 70, and having an upper mov-able pole 71, ganged with pole 68, and movable into engagement with a pair of contacts 72, 73 as pole' 68 disengages from contacts 69, 70.'

Slow-opening manual switch S1 has the movable pole 74 which is engageable with the ixed contacts 75, 76. A rst supply conductor 77 is connected to contact 76. A second supply conductor 78 is connected to one terminal 79 of vacuum pump 16. The other terminal 80 of said vacuum pump is connected by a wire 81 to switch contact 75. Thus, when switch S1 is closed, pump 16 becomes energized through a circuit comprising line wire 77, contact 76, pole 74, contact 75, wire 81, the pump motor winding, and line wire 78. Relay R1 also becomes ener,- gized through a circuit comprising line wire 77, contact 76, pole 74, contact 75, timer contacts 33 and 34, a Wire 82,`the winding of relay R1, a wire 83, switch contacts 69,`

70 and pole 68, a wire 84, lower contact 85 and lower pole 86 of relay R0, wires 133 and 87, and the line Wire 78.

Relay R1 has a holding circuit shunting the series arrangement of contacts 33, 34 and switch S1, comprising a wire 88 connected to line wire 77,`timer contacts 37,35, a wire 89,` the lower pole 90 and associated contact 91 ofthe relay R1, and a wire 92.

The energization of relay R1 will energize motor timers M1 and M3. Timer .M1 is energized through a circuit comprising line wire 78, the upperpole 93 of relay R1 and its associated contact 94, a wire 95, a wire 96, motor timer M1, a wire 97, timer contacts 39, 38, a wire 98, wire 88, and line wire 77. Timer M3 is energized by a circuit including Wire 96, motor timer M3, a wire 98', timer contacts 48,` 47, a wire 99, wire 89, timer contacts 35, 37, wire 88, and line wire 77 Relay R10, connected in parallel with timer M2 by Wires 100 and 101, likewise becomes energized.

The three-way valve solenoid 65 has an energizing circuit comprising line wire 78, wire 87, solenoid 65, a wire 102, contact 103 and pole 104 of relay R10, a wire 105, and line Wire 77. Y Y

Motor timer M3 may be energized from a circuit comprising line wire 77, motor timer M3, a Wire 105', a wire 106, upper pole 108 and associated lower contact 109 of relay R3, a wire 110, lower pole 111 and associated lower contact 112 of relay R4, a wire 113, timer contacts 43, 44, and line wire 78.

Relay R4 may be energized by a circuit including line wire 77, wire 105, the winding of relay R4, a wire 114, upper contact 115 and pole 116 of relay R3, a wire 117, wire 113, timer contacts 43, 44, and wire 78.

Relay R9 may be energized by a circuit comprising line wire 78, Wire 87, the winding of relay R0, a Wire .118, the contact 119 and pole 120 of relay R3, a wire 121, wire 105, and line wire 77.

Relay R8 may be energized by a circuit including line wire 77, wire 105, the winding of relay R0, a wire 122, and a rst branch circuit comprising upper contact 123 and pole 124 of relay R4, a wire 125, contact 126 and pole 127 of relay R3, a wire 128, lower contact 129 and pole 116 of relay R2, Wire 117, wire 113, timer contacts 43, 44, and line wire 78, `or a second branch circuit comprising upper contact130 of relay R3, pole 108, wire 106,` timer switch pole 53 and associated contact 54, a wire 131, contact 132 and pole 86 of relay R3, a wire 133, wire 87, and line wire 78.

Relay R4 has a holding circuit shunting upper contact 115 and pole,116 `of relay R2, comprising wire 114, contact 134 and pole 111 of relay R4, Wire 113 and Wire 117.

As above mentioned, the vacuum tube 58 is connected in a convention circuit, disclosed and described in detail in U.S. Patent No. 2,943,245. In this circuit alternating current supply line wire 78 is connected to the cathode 136 through resistor 138, the tube filament 139 being connected between cathode 136 and line wire 77. Screen 140 is connected to line wire 78. Control grid 57 is connected to cathode 136 through the .rheostat 56 and resistor 137. One terminal of the humidity sensing element 29 is connected by a wire 141 to the control grid 57 and the sliding tap 55, and the other terminal of sensing VVVelement 29 is connected by a wire 142 'to the line wire 7 7 4 through a condenser 143 and a resistor 144.` Asl explained in the above mentioned Patent No. 2,943,245, a negative signal in phase with the rectied current (in the plate circuit of the tube) is applied to grid 57, said signal` varying in magnitude with humidity, and the magnitude of the rectied current varies substantially inversely with humidity. Y l

The step-by-step operation of the apparatus shown in the figure is as follows:

(l) The damp mat is placed against the perforated inner face of the open cover 15.

(2) Start switch S1 is closed by depressing its'operating button. This energizes the vacuum pump16, and the mat 12 is held against the perforated inner face `of the cover by the vacuum created inside the cover.

(3) The operator then closes lthe cover 15,` which is held closed by the'spring-loaded latch 21.

(4) The closure of switch S1 also energizes the interlock relay R1 through contacts 33 and 34 of timer M1. Relay R1 energizes relay R10 and timers M1and M3.` Relay R1 is held closed by its contacts 85, 86). the energization of said timer. M1; Contacts 103,` 104 of relay R10 open, deenergizing solenoid 65.`

(5) Air from the room is drawn through the three-Way valve 27 into the tempering coil 60 in bath 28, where it is raised in temperature and passes through the humidity sensing chamber 61 and through conduit 66 into the vacuum pump. The sensing chamber 61 is thereby `condi-` tioned during the rst few seconds to the room humidity, raised tor F.

(6) As soon as timer M2 is energized, contacts44 and 43 areclosed, which energizes timer M3 through contacts 111, 112 of relay R4. also drives sliding rheostat contact 55 in a direction which causes -the plate current in the tube 58 to rise. When said plate current reaches the pull-in value of relay` R2,

said relay is energized, closing contacts 1115, 116, and relay` R4 Abecomes energized 4through said contacts 115, l 116.-`

(8) Switch S1 opens approximately 15 seconds after the initial closure thereof. When said switch opens, vacuum pump `16 becomes deenergized.

(9) After a preset `time interval (of the order of be-` tween 1 and 2 minutes) contacts 45 and 46 of timer M21 close, which reenergizes the vacuum pump through a circuit comprising line wire 77, wire 88, contacts 37, `35 of timer M1, wire 89, wire 99, contacts 45, 46 of timer M2, vacuum pump 16,-and line wire 78.`

a wire 145, wire 81, Again room air is drawn into the 4tempering coil 60.

( 10) Timer contact 47 is of sucient peripheral length approximately 3 to delay the opening of contacts 48,47 for 9 seconds after contacts 45, 46 close. When contacts 48, 47 open, timer M2 and relay R10 become deenergized. Relay contacts 1103, -104 close and solenoid 65 becomes energized, causing valve rotor 64 to turn so as to connect coil 60 to conduit 62.

(ll) Moist hot air from the dryer cover 15 is then drawn into the coil 60 and brought to a temperature of 1 110 F. The sensing element 29 responds to this high 1 humidity and causes the plate current of tube 5810 drop,

which deenergizes relay R3. (12) As the drying process continues, the air in cover -15 becomes less humid. This is detected by the sensing 90, 91 and will not release until the completion of the drying cycle (the` energization of relay R9 and the opening of its contacts Contacts 33, 34 of timer M1 open shortly afterl Timer M3c1oses contacts 53, 54` and element 29, and when the humidity in the cover air decreases to a value which is about 2% above the room air relative humidity, the accompanying increase in plate current of tube S8 causes sensitive relay R3 to pull in, energizing relay RS through contacts 126,127.

(13) Relay R9 and cover latch release solenoid 26 are energized through contacts 119, 120 of relay R8. The cover solenoid causes plunger 25 to move toward the left, as viewed in the ligure, causing latch 21 to -disengage from projection 22, releasing the cover, which swings open to the dotted view position thereof, due to the action of counterweight 20.

(14) When relay R9 is energized, contacts `85, 86 open, causing relay R1 to become deenergized, and energizing timer M3 through contacts 86 and 162 of relay R9 and contacts 53 and 54.

(l5) When relay R1 becomes deenergized, timers M1 and M2, and relay R become deenergized by the opening of contacts 94, 93. Timer contacts 45, 46 open, deenergizing the vacuum pump 16. Timer contacts 43, 44 also open, deenergizing relay R4.

(16) Relay R8 is held energized through wires 78, 87 and 133, and contacts 86, 132, 54, 53, 108 and 130. Relay R9 is held energized through contacts 120 and 119 of relay Rg.

(17) When timer M3 returns to its starting position, the follower lug on pole 53 enters notch 52, opening contacts 53, 54, .and deenergizing said timer M3 and Relay R8. When relay R8 drops out, relay R9 is thereby deenergized. This completes the drying cycle.

The manually controlled switch 67 may be employed to override the automatic humidity control means at any time, as desired. It will be seen that relay R1 can be deenergized by operating this switch to cause lower pole 68 to disengage from contacts 69, 70. Also, the engagement of upper pole 71 with contacts 72, 73 causes latch release solenoid 26 to become energized.

The structure above described and illustrated in the drawing delines a diierential system which stops the drying cycle when the cover air humidity drops to a value which is 2% above the room relative humidity. This system provides an accurate close diiferential which is not appreciably affected by variations in calibration of the humidity sensing element 29 due to aging or contamination, because the same sensing element is used for measuring both room air and cover air. Similarly, variations in the resistance of the winding of rheostat 56, in line voltage, and in the gain of the tube 58 have little or no effect on accuracy.

The differential between room and cover relative humidity can be changed by adjusting the pull-in and drop out values of relays R2 and R3, by adjusting their contact screws, or by changing over to a different range humidity sensing element 29.

While a specific embodiment of a control apparatus for a mat dryer has been disclosed in the foregoing description, it will be understood that various modifications within the spirit of the invention may occur to those skilled in the art. Therefore it is intended that no limitations be placed on the invention except as dened by the scope of the appended claims.

What is claimed is:

1. In a mat dryer, a support, a curved platen on `said support, said platen being apertured to allow air to pass therethrough, air heating means below said curved platen, a hollow cover having a perforated concave inner face adapted to iit over said platen and to receive a mat between said inner face and said platen, a vacuum pump connected to said cover, a constant temperature air tempering bath, a humidity sampling chamber in said bath, means to at times communicatively connect said chamber to said cover and at other times to connect said chamber to atmosphere,

an electrical humidity sensing element in said chamber whose resistance changes with humidity, an energizing circuit connected to said vacuum pump and including switch 5 means, means regulating the sensitivity of said switch means in accordance with the response of said sensing element when atmospheric air is admitted to said sampling chamber, and means operating said switch means in accordance with the change in resistance produced in said sensing element when the cover is subsequently connected to said chamber.

2. In a mat dryer, a support, a perforated curved platen on said support, air heating means below said curved platen, a hollow cover having a perforated concave inner face adapted to lit over said platen and to receive a mat between said inner face and platen, a vacuum pump connected to said cover, a constant temperature air tempering bath, a humidity sampling chamber in said bath, an electrical humidity sensing element in said chamber whose resistance changes with humidity, an energizing circuit connected to said vacuum pump and including relay means controlling said circuit, means -to operate said relay means responsive to changing resistance of said humidity sensing element, said relay means having a sensitivity-adjusting element, means to first connect said chamber to atmosphere, means to operate said sensitivity-adjusting element in accordance with the response of said humidity sensing element when the chamber is connected to atmosphere, whereby to condition said relay means to the humidity in the atmosphere, and means -to subsequently connect said chamber to the cover, whereby to operate said relay means in accordance with changes in humidity of the air in the cover.

3. The structure of claim 2, and means to move the cover away from said platen responsive to the operation of said relay means.

4. The structure of claim 2, and wherein the means to first connect the chamber to atmosphere and to subsequently connect the chamber to the cover comprises a three-way valve provided with an operating solenoid, said valve having an exit port connected to the chamber and respective inlet ports connected to atmosphere and to the cover, the eXit port being connected to the cover-connected port when the solenoid is energized and being connected to the atmosphere port responsive to energization ofthe solenoid, means to first simultaneously energize said pump and said solenoid, whereby to connect said chamber to atmosphere for conditioning the relay means, and means to deenergize said solenoid after a predetermined time interval, whereby to connect the chamber to the cover.

5. The structure of claim 4, and means to operate said relay means to open said energizing circuit when the humidity in the cover air decreases -to a value having a relatively small diterential with respect to the humidity in the atmospheric air, whereby to deenergize the vacuum pump.

References Cited by the Examiner UNITED STATES PATENTS FREDERICK L. MATTESON, IR., Primary Examiner.

JOHN I. CAMBY, Examiner.

D. A. TAMBURRO, Assistant Examiner. 

1. IN A MAT DRYER, A SUPPORT, A CURVED PLATEN ON SAID SUPPORT, SAID PLATEN BEING APERTURED TO ALLOW AIR TO PASS THERETHROUGH, AIR HEATING MEANS BELOW SAID CURVED PLATEN, A HOLLOW COVER HAVING A PERFORATED CONCAVE INNER FACE ADAPTED TO FIT OVER SAID PLATEN AND TO RECEIVE A MAT BETWEEN SAID INNER FACE AND SAID PLATEN, A VACUUM PUMP CONNECTED TO SAID COVER, A CONSTANT TEMPERATURE AIR TEMPERING BATH, A HUMIDITY SAMPLING CHAMBER IN SAID BATH MEANS TO AT TIMES COMMUNICATIVELY CONNECT SAID CHAMBER TO SAID COVER AND AT OTHER TIMES TO CONNECT SAID CHAMBER TO ATMOSPHERE, AN ELECTRICAL HUMIDITY SENSING ELEMENT IN SAID CHAMBER WHOSE RESISTANCE CHANGES WITH HUMIDITY, AN ENERGIZING CIRCUIT CONNECTED TO SAID VACUUM PUMP AND INCLUDING SWITCH MEANS, MEANS REGULATING THE SENSITIVITY OF SAID SWITCH MEANS IN ACCORDANCE WITH THE RESPONSE OF SAID SENSING ELEMENT WHEN ATMOSHPHERIC AIR IS ADMITTED TO SAID SAMPLING CHAMBER, AND MEANS OPERATING SAID SWITCH MEANS IN ACCORDANCE WITH THE CHANGE IN RESISTANCE PRODUCED IN SAID SENSING ELEMENT WHEN THE COVER IS SUBSTANTIALLY CONNECTED TO SAID CHAMBER. 